BIA Studies Which Only Evaluated Women

Body Composition Laboratory, U.S. Department of Agriculture/Agricultural Research Service Children’s Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA.

This article provides an overview of the present status of in vivo body composition methodologies that have potential for use in field studies. The methods are divided into four general categories: anthropometric indices and skinfold, body volume measurements, body water measurements including bioelectrical methods, and imaging techniques. Among the newest technologies are air-displacement plethysmography, three-dimensional photonic scanning, multifrequency bioelectrical impedance spectroscopy and whole-body tomography using electrical impedance and magnetic induction. These newer approaches are compared with the established reference methods. The advantages and limitations of each technique as a field method are presented relative to the corresponding concepts of an ideal method.

OBJECTIVE: To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African-American women. RESEARCH METHODS AND PROCEDURES: Fifty-five obese African-American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems, Clinton Township, MI) and DXA (Hologic QDR-2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity- and obese-specific equations were used to calculate %BF from the BIA. Bland-Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. RESULTS: Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity-specific equations had mean differences that were not significantly different from the DXA value. DISCUSSION: The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African-American women.

Journal of the American Dietetic Association. 2007 Aug;107(8):A29

Validation of Bioelectrical Impedance Against Dual-Energy X-Ray Absorptiometry in Adult, African American Females.

M.W. Valliant, D.K. Tidwell

The assessment of body composition (BC), specifically fat mass and fat-free mass is an important component of establishing nutritional status. Bioelectrical impedance (BIA) is a commonly used, non-invasive, low cost method to measure BC. African American (AA) females have a high rate of obesity so knowledge of BC is important to professionals working with this population. The objective of this study was to compare BIA (hand to foot model) to dual-energy X-ray absorptiometry (DXA) as the reference. BC was assessed by BIA (BIA 101 RJL System) and DXA (Hologic Delphi-W) in 100 healthy, AA females 18 – 40 years old with various body mass indices (range 17 – 47 kg/m2; mean = 29.53 +/- 6.86 s.d.). Both measures were completed in the morning following an overnight fast, physical inactivity for the previous 24 hours and in the supine position. Pearson.s correlation coefficient 0.94 (p = .01) indicated a strong correlation between the two methods and no significant statistical difference between the means (p = .72). Bland and Altman analysis showed strong agreement between the two methods across the range of body fat percentages indicating that they are comparable methods for measuring body fat percentage at lower and higher percentages of body fat. In conclusion, BIA is a suitable method to assess BC in adult AA females when factors such as food and beverage intake and physical activity are controlled.

Changes in body composition occur around the menopausal transition. The major characteristics are a decline in fat-free mass and an increase in body fat as a percentage of body weight. These alterations might be affected by age only or by menopause-related changes in hormone concentration. In this study the effects of tibolone, a tissue-specific compound with favorable effects on bone, vagina, and climacteric symptoms, were determined on body composition using bioelectrical impedance analysis. The focus was especially on fat mass, fat-free mass, and total body water in a group of 85 healthy women (mean +/- SD age, 54.2 +/- 4.7 yr), between 1-15 yr postmenopausal. Participants were randomly assigned to either tibolone (2.5 mg; n = 42) or identically appearing placebo tablets (n = 43) daily for 12 months. All analyses were based on the intent to treat group and last visit. Compared with placebo, tibolone significantly increased fat-free mass by 0.85 kg (P = 0.003) and total body water by 0.78 liter (P = 0.001). No significant difference was observed on the fat mass parameter (P = 0.16). From these results it can be concluded that tibolone may counteract the postmenopausal changes in body composition.

OBJECTIVE: To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African-American women. RESEARCH METHODS AND PROCEDURES: Fifty-five obese African-American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems, Clinton Township, MI) and DXA (Hologic QDR-2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity- and obese-specific equations were used to calculate %BF from the BIA. Bland-Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. RESULTS: Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity-specific equations had mean differences that were not significantly different from the DXA value. DISCUSSION: The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African-American women.

Am J Clin Nutr. 1999 Jul;70(1):5-12.

Body-composition changes with diet and exercise in obese women: a comparison of estimates from clinical methods and a 4-component model.

Departments of Exercise Science and Foods and Nutrition, The University of Georgia, Athens, USA. eevans@imgate.wustl.edu

BACKGROUND: Most methods available to clinicians for estimating body-composition changes have been validated against estimates from densitometry, based on a 2-component (fat mass and fat-free mass) model. OBJECTIVE: Estimates of changes in percentage body fat (%BF) from dual-energy X-ray absorptiometry (DXA), skinfold thicknesses (SFTs), bioelectrical impedance analysis (BIA), and body mass index (BMI; in kg/m2) were compared with estimates from a 4-component (fat, water, mineral, and protein) model (%BFd,w,m), a more accurate method. DESIGN: Determinations of body density from hydrostatic weighing, body water from deuterium dilution, bone mineral and %BF from whole-body DXA, resistance from BIA, and anthropometric measures were made in 27 obese women (BMI: 31.1 +/- 4.9) assigned to 1 of 3 groups: control (C; n = 9), diet only (DO; n = 9), or diet plus aerobic exercise (DE; n = 9). RESULTS: After the 16-wk intervention, changes in body mass (BM) averaged 0.5 +/- 2.0, -7.2 +/- 7.4, and -4.0 +/- 3.3 kg and changes in %BFd,w,m averaged 2.1 +/- 1.0%, -1.2 +/- 1.4%, and -2.4 +/- 1.6% in the C, DO, and DE groups, respectively. Compared with changes in %BFd,w,m, the errors (SD of bias) for estimates of changes in %BF by DXA, BIA, SFTs, and BMI were similar (range: +/-2.0-2.4% of BM). BIA, SFTs, and BMI provided unbiased estimates of decreases in %BFd,w,m, but DXA overestimated decreases in %BF in the DO and DE groups. CONCLUSIONS: DXA, BIA, SFTs, and BMI are comparably accurate for evaluating body-composition changes induced by diet and exercise interventions; however, small changes in %BF may not be accurately detected by these clinical methods.

These papers and abstracts of papers have been published in peer-reviewed journals. They may draw conclusions and discuss applications of Bioelectrical Impedance Analysis which have not been reviewed by the FDA. Statements made within them are the sole responsibility of the authors. Unless otherwise indicated, no material support was provided to the authors or study investigators by RJL Systems.